This invention relates to needle-less injectors, and, in particular, to engine and diffuser assemblies for use with modular gas-pressured needle-less injectors and methods of performing needle-less injections using the same.
Traditionally, fluids such as medications are injected into patients, either subdermally or intradermally, using hypodermic syringe needles. The body of the syringe is filled with the injectable fluid and, once the needle has pierced the patient""s skin, the syringe plunger is depressed so as to expel the injectable fluid out of an opening in the needle. The person performing the injection is usually a trained medical services provider, who manually inserts the hypodermic needle between the layers of a patient""s skin for an intradermal injection, or beneath the skin layers for a subcutaneous injection.
Intradermal or subdermal delivery of a medication through the use of a hypodermic needle requires some skill and training for proper and safe administration. In addition, the traditional method of intradermal injections requires actual physical contact and penetration of a needle through the skin surface of the patient, which can be painful for the patient. Traditional needle injectors, such as hypodermic syringes, are also expensive to produce and difficult to use with prepackaged medication doses. Needle injectors also suffer from increased danger of contamination exposure to health care workers administering the injections, and to the general public when such injectors are not properly disposed of.
Jet injectors are generally designed to avoid some or all of these problems. However, not only are conventional jet injectors cumbersome and awkward, but, existing conventional jet injectors are only capable of subcutaneous delivery of a medication beneath the skin layers of a patient. Conventional jet injectors are also somewhat dangerous to use, since they can be discharged without being placed against the skin surface. With a fluid delivery speed of about 800 feet per second (fps) and higher, a conventional jet injector could injure a person""s eye at a distance of up to 15 feet. In addition, jet injectors that have not been properly sterilized are notorious for creating infections at the injection site. Moreover, if a jet injector is not positioned properly against the injection site, the injection can result in wetting on the skin surface. Problems associated with improper dosage amounts may arise as well, if some portion of the fluid intended for injection remains on the skin surface following an injection, having not been properly injected into and/or through the skin surface.
Typically, needle-less medication injectors use either an expansion spring or a compressed inert gas to propel the fluid medication (via a push rod plunger) through a small orifice (an injector nozzle) which rests perpendicular to and against the injection site. The fluid medication is generally accelerated at a high rate to a speed of between about 800 feet per second (fps) and 1,200 fps (approximately 244 and 366 meters per second, respectively). This causes the fluid to pierce through the skin surface without the use of a needle, resulting in the medication being deposited in a flower pattern under the skin surface.
It should be noted, however, that compression spring propelled jet injectors do not offer linear delivery speeds (constant speed of the fluid being injected). In addition to this problem, spring propelled jet injectors with weak (e.g., deteriorated) springs often slow fluid delivery speed down while an injection is being administered, resulting in improper fluid penetration. Reduced speed of the fluid can cause improper dosing and bruising at the injection site when the injection surface is the skin of a human recipient.
In a jet injector, if the inert gas is not quickly and properly expelled, fluid may be improperly injected, as with those devices employing a compression spring. Conventional disposable needle-less injectors, such as those shown in U.S. Pat. No. 4,913,699 to Parsons and U.S. Pat. No. 5,009,637 to Newman et al. show a gas-containing, breakable tube that is shattered or cracked open by a side mounted trigger. Difficulties arise in the need to maintain tight tolerances on the breakable member, since minor changes in thickness can dramatically effect the pressure needed to deploy the gas from the gas chamber of the device. In addition, the broken shards of the breakable member are ejected at high speed when the gas is expelled and these shards can occasionally jam between the plunger driver and the housing, thereby preventing proper operation of the needle-less injector. Attempts to prevent small shards from being formed would obviate some of this potential, but tend to make activation of the device more difficult.
U.S. Pat. Nos. 6,080,130, 6,063,053, 5,851,198 and 5,730,723 describe needle-less injectors incorporating a gas power source, thus obviating some of the limitations inherent in compression spring injectors and addressing many of the concerns of conventional jet injectors. The injectors described therein have a pre-filled and self-contained compressed gas for providing pressure to inject medication into the skin surface of a patient without the use of a needle.
Gas power sources for needle-less injectors that employ either pop valves or breakaway tab valves to release the inert gas stored in their respective gas chambers, however, may only be opened once, thereby presenting difficulty with regard to quality control testing measures. Further, operation of many injectors requires a user to depress a trigger, relying mainly on resistance force from the injection surface to initiate an injection. Where the underlying surface is sensitive, applying such pressure may not be advantageous. Further, if the injection surface is slippery such a device may slide out of place during an injection rendering its use potentially injurious and possibly resulting in improper fluid delivery.
U.S. patent application Ser. No. 09/834,476 describes a needle-less injector that includes an engine assembly fit with a diffuser. The diffuser includes a number of channels which allow gas deployed from the engine to pass from the storage canister through the diffuser to the distal end of a driver, forcing the driver forward and causing liquid to be expelled from the injector. The number, orientation and size of these channels may be selected to optimize delivery parameters of a particular injection fluid. However, the use of channels in a diffuser may result in excessive back pressure upon deployment of gas from the engine. Consequentially, optimal gas flow may not be achieved, and the injector may not operate in the most efficient manner possible. Suboptimal gas flow may result in a comparatively slower injection; shallower liquid penetration into the patient; and moderate pain upon administration of an injection.
U.S. patent application Ser. No. 09/834,476 further describes grips configured upon the engine assembly that mechanically interlock with a diffuser. The interlocking action occurs upon administration of an injection, as the engine assembly travels axially forward relative to the diffuser, which remains stationary. A user must apply a significant degree of mechanical force to cause this interlocking action to take place. Moreover, upon mechanical interaction of the grips and diffuser, an unpleasant xe2x80x9cclickingxe2x80x9d sound may be heard.
It is therefore an object of an embodiment of the instant invention to provide gas-pressured needle-less injectors that obviate, for practical purposes, the above-mentioned limitations.
In one embodiment of the instant invention, a needle-less injector suitable for injecting fluid through an injection surface includes a housing, a trigger, an engine, a diffuser, and a driver. The housing contains a fluid and the engine contains a compressed gas. Upon application of a sufficient amount of force to the trigger, the compressed gas is released from the engine forcing the driver through the interior of the housing, expelling the fluid from the housing at a speed sufficient to pierce an injection surface.
In another embodiment of the instant invention, a diffuser suitable for use with a needle-less injector includes an unobstructed air passage that may further include aerodynamic fins. The aerodynamic fins facilitate in the creation and maintenance of air flow with negligible back pressure when compressed gas is forced through the unobstructed air passage of the diffuser.
In another embodiment of the instant invention, a needle-less injector suitable for injecting fluid through an injection surface includes an engine, a diffuser, and a driver. The diffuser may include an unobstructed air passage that may further include aerodynamic fins. The engine contains a compressed gas, and the aerodynamic fins facilitate in the creation and maintenance of air flow with negligible back pressure when compressed gas is forced through the unobstructed air passage of the diffuser.
In another embodiment of the instant invention, a needle-less injector suitable for injecting fluid through an injection surface includes an engine, a diffuser, and a driver. The diffuser may include an O-ring around its outer circumference. The engine contains a compressed gas, and the O-ring prevents undesirable leakage of gas through the space between the engine and the diffuser.
In another embodiment of the instant invention, the needle-less injector includes a mechanism for mitigating the kickback associated with releasing compressed gas from the engine. Grips may be included on the engine, mechanically coupling the engine to a diffuser that is affixed to the housing, thereby preventing the engine from separating from the housing upon release of compressed gas from the engine. Retainer hooks on the interior of the trigger corresponding to latch retainer mechanisms on the exterior of the housing may also be used to prevent the engine from separating from the housing.
In yet another embodiment of the instant invention, the housing of the needle-less injector includes finger rests that provide stability in administering an injection and provide resistance to activate the needle-less injector. Thus, a user need not rely solely on resistance from the injection surface to initiate the administration of an injection. The finger rests may be included on opposing sides of the housing, designed to comfortably receive the fingers of a user without substantial slippage.
In yet another embodiment of the instant invention, the engine of the needle-less injector is fitted with a reusable valve. The valve may contain a rubber head that is held against a fixed element of the engine, such as an airtight ring, such that depression of the trigger separates the head from the fixed element, releasing the compressed gas from the engine and, further, forcing the driver to expel fluid from the housing. A spring may be included in the valve to help maintain a proper airtight seal with the canister holding the compressed gas.
In yet another embodiment of the instant invention, a safety clamp is included on the exterior of the housing of the needle-less injector, preventing accidental activation of the device. The safety clamp must be removed prior to use and may be made of a sufficiently elastic material such that a user need only deform the clamp, aided by grips included thereon, to remove the clamp from the housing.